Optical fiber ribbon bonded portion flattening system, optical cable manufacturing method, and optical cable manufactured using same

Abstract

The present invention relates to an optical fiber ribbon bonded portion flattening system and a rollable optical fiber ribbon manufactured thereby, the system having an appropriate vertical separation strength at each bonded portion of a rollable optical fiber ribbon, and minimizing deviation of the vertical separation strength at each bonded portion in the longitudinal direction and the width direction of an optical fiber, thereby providing a uniform and sufficient bonding force between the bonded portion and the optical fiber so that the shape of the rollable optical fiber ribbon can be maintained and damage to the optical fiber can be prevented.

Description

Optical fiber ribbon joint flattening system and optical cable manufacturing method, optical cable manufactured thereby

[0001] The present invention relates to a flattening system for optical fiber ribbon joints, a method for manufacturing an optical cable, and an optical cable manufactured thereby. More specifically, the present invention relates to a flattening system for optical fiber ribbon joints and a method for manufacturing an optical cable, and an optical cable manufactured thereby, which can maintain the shape of a rollable optical fiber ribbon and prevent damage to the optical fiber by having appropriate vertical separation strength at each joint of a rollable optical fiber ribbon and minimizing the deviation of vertical separation strength at each joint in the optical fiber length direction and width direction, thereby providing a uniform and sufficient bonding force between the joint and the optical fiber.

[0002] Recently, as the demand for ultra-high-speed communication has increased, the demand for optical cable-based communication networks has also been continuously rising. Optical cables are advantageous for constructing ultra-high-speed transmission networks due to their high bandwidth and small weight and volume.

[0003] To construct a high-capacity optical communication network, an optical cable may be used that accommodates multiple optical ribbons aggregated by splicing multiple optical fibers side by side inside the cable. In particular, a rollable optical ribbon accommodated in a high-density optical cable may have a structure in which adjacent optical fibers among the multiple optical fibers can roll in the width direction through splicings intermittently arranged along the length direction.

[0004] Such rollable optical fiber ribbons must be uniformly bonded with a vertical separation strength sufficient to prevent damage to the outer surface of the optical fibers when separating bonded optical fibers during the connection process, so that the bonded optical fibers do not easily separate while maintaining the shape of the ribbon even when rolled in the width direction.

[0005] Meanwhile, the joint of the rollable optical fiber ribbon can be formed in the area between the pair of optical fibers by spraying bonding resin from a resin dispenser into the boundary area of ​​an adjacent pair of optical fibers during the manufacturing process of the rollable optical fiber ribbon, and then curing the bonding resin.

[0006] Figure 1 illustrates an example of bonding resin being sprayed from a resin dispenser onto a pair of adjacent optical fiber boundary regions.

[0007] FIG. 1(a) illustrates a case where bonding resin (20r) is normally sprayed onto the surface of an optical fiber (10) from a resin dispenser (520). Normal spraying means that the bonding resin (20r) is sprayed into the center of the boundary region of an adjacent pair of optical fibers (10).

[0008] FIG. 1(b) illustrates a case where bonding resin (20r) is sprayed eccentrically from a resin dispenser (520). Eccentric spraying means that the bonding resin (20r) is sprayed in a direction biased toward one of the adjacent pair of optical fibers (10) boundary regions. Such eccentric spraying may be caused by various factors, such as deviations in the spray angle due to the viscosity of the resin.

[0009] When bonding resin (20r) is sprayed eccentrically onto the surface of one of the adjacent pair of optical fibers (10) from a resin dispenser (520) as shown in FIG. 1(b) to form a bonding portion (20) of a rollable optical fiber ribbon, the bonding area between the bonding portion (20) and each optical fiber (10) is not uniform. That is, the bonding portion may be formed excessively biased toward one of the adjacent pair of optical fibers (10) (10'), and the bonding area may be insufficient for the other optical fiber (10''). As a result, the difference in bonding strength between each optical fiber (10) and the bonding part (20) increases, so the optical fiber (10'') with insufficient bonding area with the bonding part (20) is easily separated even at low separation strength and cannot maintain the shape of the rollable optical fiber ribbon, and the optical fiber (10') with excessive bonding area with the bonding part (20) requires high separation strength, so the problem of damage to the optical fiber (10'), such as the curling layer being torn off, may occur.

[0010] Therefore, there is a great demand for a fiber optic ribbon joint flattening system and a rollable fiber optic ribbon manufactured thereby, which can maintain the shape of the rollable fiber optic ribbon (100) and prevent damage to the fiber optic (10) by having appropriate vertical separation strength at each joint (20) and minimizing the deviation of vertical separation strength at each joint (20) in the optical fiber length direction and width direction, thereby providing a uniform and sufficient bonding force between the joint (20) and the optical fiber (10).

[0011] The present invention aims to solve the problem of providing an optical fiber ribbon joint flattening system and an optical cable manufacturing method that can maintain the shape of a rollable optical fiber ribbon and prevent damage to the optical fiber by having appropriate vertical separation strength at each joint of the rollable optical fiber ribbon and minimizing the deviation of vertical separation strength at each joint in the optical fiber length and width directions, thereby providing a uniform and sufficient bonding force between the joint and the optical fiber.

[0012] To solve the above problem, the present invention may provide an optical cable comprising: an optical cable core including a plurality of optical fiber ribbons; and a cable jacket surrounding the optical cable core; wherein the optical fiber ribbon comprises an optical fiber assembly in which a plurality of optical fibers are arranged side by side, the optical fiber ribbon comprising a core, a clad layer surrounding the core, and one or more coating layers surrounding the clad layer; and a plurality of junctions intermittently arranged along the longitudinal direction between adjacent pairs of optical fibers among the plurality of optical fibers included in the optical fiber assembly; wherein the outer surface that does not directly contact the optical fibers of the junctions in a cross-section perpendicular to the longitudinal direction of the optical fiber assembly includes a flattened portion.

[0013] Here, the highest point of the junction may be positioned above a connected straight reference line that simultaneously contacts each outer surface of a pair of optical fibers on both sides of the junction.

[0014] In addition, the outer surface of the joint may include a curved shape.

[0015] In addition, the outer surface of the joint may include a smooth portion and two connecting portions disposed on each side of the smooth portion.

[0016] Here, the radius of curvature of the smooth portion of the joint may be larger than the radius of curvature of the connecting portion.

[0017] In this case, the junction may be positioned to surround at least a portion of the circumference of each optical fiber joined through the junction in the region between an adjacent pair of optical fibers.

[0018] In addition, in the longitudinal and perpendicular cross-sections of the optical fiber, the ratio of the junction cross-sectional area of ​​[Equation 1] below to the circumference of any one of the pair of optical fibers joined by the junction may be in the range of 47% to 84%.

[0019] [Equation 1]

[0020] Cross-sectional area of ​​the junction = Length of the inner surface where the junction contacts the outer circumference of one optical fiber (ℓ1) + Length of the inner surface where the junction contacts the outer circumference of another optical fiber (ℓ2) + Length of the outer surface of the portion where the junction does not contact the optical fiber (ℓ3)

[0021] In addition, the vertical separation strength of the junction placed between the optical fiber pairs provided in the optical fiber ribbon may be 2gf to 10gf.

[0022] In addition, the longitudinal standard deviation (σl) of the vertical separation strength of a plurality of joints spaced apart in the longitudinal direction between the optical fiber pairs provided in the optical fiber ribbon may be 2.0 or less, preferably 1.0 or less.

[0023] Here, the width direction standard deviation (σ) of the vertical separation strength of the junctions respectively disposed between the plurality of optical fiber pairs provided in the optical fiber ribbon l ) can be 2.0 or less, preferably 1.0 or less.

[0024] In this case, the arithmetic average roughness (Ra) of the JIS B0601 standard of the smooth portion formed on the outer surface of the joint may be 2 micrometers (μm) or less.

[0025] And, the height difference (H) from the highest point of the junction based on a straight reference line (L) connected by simultaneously contacting each outer surface of a pair of optical fibers on both sides of the junction. UP ) is 5 micrometers (μm) to 30 micrometers (μm) or less, and the height difference (H) from the lowest point DN ) can also be 30 micrometers (μm) or less.

[0026] Here, the height difference (H) from the lowest point of the junction is based on a straight reference line (L) connected by simultaneously contacting the outer surfaces of each of the pair of optical fibers on both sides of the junction. DN) can be 5 micrometers (μm) to 30 micrometers (μm).

[0027] In addition, the angle formed by the line connecting the end of each connection formed on the outer surface of the joint and the center of the optical fiber, and the line perpendicularly connected to the straight reference line that simultaneously contacts the outer surface of each pair of optical fibers on both sides of the joint from the center of each optical fiber, may be in the range of -30 degrees (˚) to -1 degree (˚).

[0028] In addition, the angle formed by the line connecting the end of each connection formed on the outer surface of the joint and the center of the optical fiber, and the line perpendicularly connected to the straight reference line that simultaneously contacts the outer surface of each pair of optical fibers on both sides of the joint from the center of each optical fiber, may be in the range of 1 degree (˚) to 40 degrees (˚).

[0029] In addition, to solve the above problem, the present invention may include an optical fiber ribbon joint flattening system characterized by comprising: an optical fiber supply line that supplies a plurality of optical fibers in a predetermined direction while the plurality of optical fibers constituting the optical fiber ribbon are arranged parallel along the longitudinal direction; a resin dispenser disposed in an upper region of the optical fiber supply line and spraying a bonding resin toward the optical fiber boundary region; a flattening cover die disposed in the optical fiber supply line and flattening the surface of the bonding resin; and a resin curing device disposed in an upper region of the optical fiber supply line and curing the sprayed bonding resin.

[0030] And, the flattening cover die may include: a lower cover die that supports a plurality of optical fibers moving along the optical fiber supply line from below and is positioned on the optical fiber supply line; and an upper cover die that is positioned above the lower cover die and faces the lower cover die in an upward and downward direction.

[0031] Here, the lower cover die is installed at a fixed position so that its relative position with respect to the optical fiber supply line is maintained at a constant level, and an optical fiber receiving groove is formed in the central part of the lower cover die to accommodate a plurality of optical fibers in a seated state, and the upper cover die may have an optical fiber cover groove formed to cover the upper area of ​​the plurality of optical fibers accommodated in the optical fiber receiving groove of the lower cover die.

[0032] In this case, the optical fiber receiving groove of the lower cover die and the optical fiber cover groove of the upper cover die are formed so that their cross-sectional widths correspond to each other, and a void space through which a plurality of optical fibers can pass can be formed between the optical fiber receiving groove and the optical fiber cover groove when the lower cover die and the upper cover die face each other.

[0033] And, the height of the above empty space may be larger than the outer diameter of the optical fiber.

[0034] In addition, the optical fiber cover groove of the upper cover die can be positioned higher than the optical fiber.

[0035] In addition, a void space is formed in the flattening cover die through which a plurality of optical fibers can pass, the height of the void space is greater than the outer diameter of the optical fiber, and the upper surface of the void space may be positioned higher than the optical fiber.

[0036] In addition, when the plurality of optical fibers consists of N optical fibers (N is a natural number greater than or equal to 2), the resin dispenser may be provided in (N-1) units.

[0037] To solve the above problem, the present invention provides a method for manufacturing an optical cable comprising: a fiber ribbon manufacturing step of joining a plurality of optical fibers in parallel by forming a plurality of joints at spaced positions between a plurality of adjacent optical fibers; a fiber cable core forming step of assembling the plurality of fiber ribbons formed in the fiber ribbon manufacturing step; and a cable jacket covering step of supplying the fiber cable core formed in the fiber cable core forming step and covering the cable jacket; wherein the fiber ribbon manufacturing step comprises: a fiber supply step of supplying a plurality of optical fibers in a predetermined direction to a fiber supply line while the plurality of optical fibers are arranged parallel along the length direction; a resin injection step of injecting a bonding resin between a plurality of adjacent pairs of optical fibers; a joint forming step of flattening the surface of the bonding resin injected between the plurality of adjacent pairs of optical fibers; and a resin curing step of forming a joint by irradiating heat or ultraviolet (UV) light with a resin curing device onto the bonding resin with the flattened surface.

[0038] Here, in the joint forming step, the highest point of the joint can be flattened so as to be positioned above a connected straight reference line while simultaneously contacting each outer surface of a pair of optical fibers on both sides of the joint.

[0039] In addition, in the optical cable core forming step, the plurality of optical fiber ribbons may be divided into a plurality of tube members or binders and assembled to form a plurality of optical units, and the plurality of optical units may be assembled to form the optical cable core.

[0040] In addition, the above joint forming step can be manufactured by a flattening cover die applying pressure to the bonding resin.

[0041] Here, the flattening cover die may include: a lower cover die that supports a plurality of optical fibers moving along the optical fiber supply line from below and is positioned on the optical fiber supply line; and an upper cover die that is positioned above the lower cover die and faces the lower cover die in an upward and downward direction.

[0042] In this case, as the plurality of optical fibers pass through the space between the lower cover die and the upper cover die, the surface of the bonding resin sprayed onto the plurality of optical fibers can be flattened.

[0043] In addition, the lower cover die is installed at a fixed position so that its relative position with respect to the optical fiber supply line is maintained at a constant level, and an optical fiber receiving groove is formed in the central part of the lower cover die to accommodate a plurality of optical fibers in a seated state, and the upper cover die may have an optical fiber cover groove formed to cover the upper area of ​​the plurality of optical fibers accommodated in the optical fiber receiving groove of the lower cover die.

[0044] In addition, the optical fiber receiving groove of the lower cover die and the optical fiber cover groove of the upper cover die are formed such that their cross-sectional widths correspond to each other, and a void space through which a plurality of optical fibers can pass can be formed between the optical fiber receiving groove and the optical fiber cover groove when the lower cover die and the upper cover die face each other.

[0045] And, the outer surface of the joint of the optical fiber ribbon flattened by the flattening cover die may be pressed to form a curved shape, having a smooth portion and two connecting portions respectively disposed on both sides of the smooth portion.

[0046] Here, the magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die can be controlled so that the arithmetic average roughness (Ra) of the smooth portion formed on the outer surface of the junction according to JIS B0601 standard is 2 micrometers (μm) or less.

[0047] In this case, one or more coating layers of the optical fiber include a coloring layer as the outermost layer, and the optical fiber ribbon manufacturing step may be performed in a process atmosphere in which the oxygen concentration of the optical fiber is 300 ppm or less.

[0048] In this case, the magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die is the height difference (H) between the highest point of the junction and the straight reference line (L) connected by simultaneously contacting each outer circumference of a pair of optical fibers on both sides of the junction. UP ) can be controlled to be 30 micrometers (μm) or less.

[0049] In addition, the magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die is the height difference (H) from the lowest point of the junction based on a straight reference line (L) connected by simultaneously contacting each outer circumference of a pair of optical fibers on both sides of the junction. DN ) can also be controlled to be 30 micrometers (μm) or less.

[0050] In addition, the magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die can be controlled so that the angle formed by the line connecting the end of each connection formed on the outer surface of the junction and the center of the optical fiber, and the line perpendicularly connected to the straight reference line that simultaneously contacts the outer circumference of each pair of optical fibers on both sides of the junction from the center of each optical fiber, is -30 degrees (˚) to -1 degree (˚).

[0051] In addition, the magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die can be controlled so that the angle formed by the line connecting the end of each connection formed on the outer surface of the junction and the center of the optical fiber, and the line perpendicularly connected to the straight reference line that simultaneously contacts the outer surface of each pair of optical fibers on both sides of the junction from the center of each optical fiber, is in the range of 1 degree (˚) to 40 degrees (˚).

[0052] According to the optical fiber ribbon joint flattening system and optical cable manufacturing method according to the present invention, and the optical cable manufactured thereby, by flattening the joint surface using a flattening cover die, the joint forms a uniform joint along the outer surface of each optical fiber in the region between a pair of optical fibers, thereby minimizing the vertical separation strength required to vertically separate a pair of optical fibers joined together along the optical fiber length direction, the horizontal separation strength required to horizontally separate them, or the deviation between the vertical separation strength and the horizontal separation strength. Accordingly, the problem of unintended separation of optical fibers in a rollable optical fiber ribbon can be prevented, and damage to the optical fibers can be prevented during the optical fiber separation process.

[0053] In addition, according to the optical fiber ribbon joint flattening system and optical cable manufacturing method according to the present invention, the optical cable manufactured thereby, by flattening the joint surface using a flattening cover die, forms a joint having a uniform appearance, thereby improving the appearance quality of the rollable optical fiber ribbon and maintaining the shape of the rollable optical fiber ribbon.

[0054] Furthermore, according to the optical fiber ribbon joint flattening system and optical cable manufacturing method of the present invention, and the optical cable manufactured thereby, even if the oxygen content of the optical fiber surface coloring layer is lowered, excellent bonding strength is provided by optimizing the ratio of the cross-sectional area of ​​the joint to the circumference of the optical fiber, and damage to the coloring layer can be prevented by effectively controlling the oxygen concentration.

[0055] Figure 1 illustrates an example of bonding resin being sprayed between a pair of optical fibers constituting a rollable optical fiber ribbon through a resin dispenser.

[0056] FIG. 2 illustrates a cross-sectional view of one example of a multi-core optical cable according to the present invention.

[0057] FIG. 3 illustrates one embodiment of an optical fiber ribbon joint flattening system according to the present invention.

[0058] FIG. 4 shows a cross-sectional view of a flattening cover die of an optical fiber ribbon joint flattening system according to the present invention.

[0059] FIG. 5 illustrates a cross-sectional view of a state in which the surface of a joint is flattened through a flattening cover die constituting a fiber optic ribbon joint flattening system according to the present invention.

[0060] FIG. 6 illustrates a plan view of a rollable optical fiber ribbon constituting an optical cable according to the present invention.

[0061] FIG. 7 illustrates a vertical separation strength measuring device for measuring vertical separation strength at a joint of a rollable optical fiber ribbon constituting an optical cable according to the present invention.

[0062] Figure 8 illustrates the extraction of a rollable optical fiber ribbon specimen and a plurality of optical fiber pair specimens from a rollable optical fiber ribbon.

[0063] FIGS. 9 to 15 illustrate enlarged cross-sectional views showing various embodiments of an optical fiber and a joint constituting a rollable optical fiber ribbon constituting an optical cable according to the present invention in the AA' cross-section of FIG. 6.

[0064] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the spirit of the invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components.

[0065] FIG. 2 illustrates a cross-sectional view of one example of a multi-core optical cable according to the present invention.

[0066] The optical cable (100) illustrated in FIG. 2 has an optical cable core (C) comprising a plurality of optical fiber ribbons accommodated inside a jacket (80). The core (C) includes a plurality of optical fibers (11), and the plurality of optical fibers (11) may be configured in the form of one or more optical units (10) assembled by means such as binding yarn, binding tape, or tube.

[0067] As shown in FIG. 2, to reinforce the tensile strength and rigidity of the cable, a central tension line (1) is provided at the center of the cable and optical units (10) are arranged circumferentially around it to form a core (C), or a reinforcing member (70) is embedded in a jacket (80) that surrounds the core (C) composed of multiple optical units (10) without the central tension line (1), or the central tension line (1) and the reinforcing member (70) may be applied together.

[0068] The above central tension line (1) and the above reinforcing member (70) may be made of materials such as FRP, aramid yarn, etc.

[0069] In addition, the core (C) can be configured by wrapping a plurality of optical units (10) with a binding tape or other assembly member (50), and can be covered with a jacket (80) to form an optical cable (100).

[0070] In addition, the core (C) may be provided with a rip cord (60) for removing the jacket (80) between the assembly member (50) and the jacket (80).

[0071] The above rip cord (60) may be provided to remove the jacket when connecting the optical cable. The above rip cord (60) may be configured in the form of a fiber, and a pair may be provided in one place or at symmetrical positions as shown in FIG. 2.

[0072] First, in order to connect or branch the optical cable, the jacket must be stripped to a certain length, and the worker may cut the end of the jacket with a cutter or similar tool to expose at least a portion of the rip cord in order to strip the jacket to a certain length.

[0073] When the above rip cord is exposed at the end of the optical cable, the operator can pull the rip cord to cut the jacket to an appropriate length and remove the jacket from the cut portion to expose the core of the optical cable.

[0074] Additionally, the optical cable according to the present invention comprises: an optical cable core (C) including a plurality of optical fiber ribbons (15); and a cable jacket (80) covering the optical cable core (C); wherein the optical fiber ribbons (15) comprise an optical fiber assembly in which a plurality of optical fibers (11) are arranged side by side, each comprising a core, a clad layer covering the core, and one or more coating layers covering the clad layer; and a plurality of junctions (20, see FIG. 5) intermittently arranged along the longitudinal direction between adjacent pairs of optical fibers among the plurality of optical fibers included in the optical fiber assembly; and wherein the outer surface that does not come into direct contact with the optical fibers of the junctions (20) in the longitudinal and perpendicular cross-section of the optical fiber assembly may be configured to include a flattened portion.

[0075] Meanwhile, the above-mentioned joint (20) may have a shape in which at least a portion of the outer surface is flattened using a flattening cover die (400) described later. If the flattening cover die (400) is pressed down to a straight reference line (L), a defect may occur in which the bonding resin is pushed in the width direction of the optical fiber ribbon (15) and encroaches into an unintended area, as shown in FIG. 10. Therefore, the highest point of the above-mentioned joint (20) may be positioned above the straight reference line (L) connected by simultaneously contacting each outer surface of a pair of optical fibers (11) located on both sides of the above-mentioned joint (20).

[0076] An optical cable according to the present invention may be manufactured by a method for manufacturing an optical cable comprising: an optical fiber ribbon manufacturing step of joining a plurality of optical fibers in parallel by forming a plurality of joints at spaced positions between a plurality of adjacent optical fibers; an optical cable core forming step of assembling the plurality of optical fiber ribbons formed in the optical fiber ribbon manufacturing step; and a cable jacket covering step of supplying the optical cable core formed in the optical cable core forming step and covering the cable jacket; wherein the optical fiber ribbon manufacturing step comprises: an optical fiber supply step of supplying a plurality of optical fibers in a predetermined direction to an optical fiber supply line while the plurality of optical fibers are arranged parallel along the length direction; a resin injection step of injecting a bonding resin between a plurality of adjacent optical fiber pairs of the plurality of optical fibers; a joint forming step of flattening the surface of the bonding resin injected between the plurality of adjacent optical fiber pairs; and a resin curing step of forming a joint by irradiating heat or ultraviolet (UV) light with a resin curing device onto the bonding resin with the flattened surface.

[0077] Here, in the optical cable core forming step, the plurality of optical fiber ribbons (15) are divided into a plurality of tube members or binders and assembled to form a plurality of optical units (10), and the plurality of optical units (10) can be assembled to form the optical cable core (C).

[0078] In addition, the above-mentioned joint forming step can be manufactured by a flattening cover die applying pressure to the bonding resin. This will be explained in detail with reference to FIG. 3 and below.

[0079] FIG. 3 illustrates one embodiment of an optical fiber ribbon joint flattening system according to the present invention.

[0080] As illustrated in FIG. 3, the optical fiber ribbon joint flattening system (1000) according to the present invention may be configured to include: an optical fiber supply line (510) that supplies a plurality of optical fibers (10) constituting a rollable optical fiber ribbon in a predetermined direction while the plurality of optical fibers (10) are arranged parallel along the longitudinal direction; a resin dispenser (520) disposed in the upper region of the optical fiber supply line (510) and sprays a bonding resin (20r) onto the boundary region of the optical fibers (10); a resin curing device (530) disposed in the upper region of the optical fiber supply line (510) and cures the bonding resin (20r) sprayed onto the boundary region of the optical fibers (10) through the resin dispenser (520); and a flattening cover die (400) disposed in the optical fiber supply line (510) and flattening the surface of the bonding resin (20r).

[0081] The optical fiber supply line (510) is a path through which a plurality of optical fibers (10) constituting a rollable optical fiber ribbon (100) are supplied. The plurality of optical fibers (10) are transported and supplied along the optical fiber supply line (510) in a state where they are arranged parallel to each other in the direction of the optical fiber length.

[0082] The optical fiber supply line (510) pulls and unwinds a plurality of optical fibers (10) from each optical fiber bobbin with constant tension, thereby allowing the plurality of optical fibers (10) to be transported in parallel along the optical fiber supply line (510) at a constant speed, and to be transported to an accurate position at the bottom of the resin dispenser (520) or the resin curer (530).

[0083] A plurality of resin dispensers (520) may be provided in the upper region of the optical fiber supply line (510). The resin dispensers (520) have nozzles positioned toward the optical fiber supply line (510) so that bonding resin (20r) stored in the resin dispensers (520) can be sprayed into the boundary region of the optical fiber (10).

[0084] A plurality of resin dispensers (520) can spray bonding resin (20r) between adjacent pairs of optical fibers (10) among a plurality of optical fibers (10) arranged side by side, and the number or arrangement of the resin dispensers (520) is adjusted so as to effectively perform this resin spraying function.

[0085] In addition, the resin dispenser (520) can adjust the spray interval, spray amount, and spray position.

[0086] Meanwhile, when the plurality of optical fibers (10) included in the rollable optical fiber ribbon (100) consists of N optical fibers (10) (N is a natural number greater than or equal to 2), the resin dispenser (520) may be provided with (N-1) resin dispensers (520) to spray bonding resin in each area between mutually adjacent pairs of optical fibers among the N optical fibers (10) constituting the rollable optical fiber ribbon (100).

[0087] The resin curing device (530) is positioned in the upper region of the optical fiber supply line (510). The resin curing device (530) performs the function of curing the bonding resin (20r) sprayed from the resin dispenser (520) or the bonding resin (20r) whose surface has been flattened by passing through the flattening cover die (400) with heat or ultraviolet (UV).

[0088] When the bonding resin (20r) is exposed to ultraviolet rays or heat through the above resin curing device (530), the bonding resin (20r) is cured and the bonding portion (20) of the rollable optical fiber ribbon (100) is formed.

[0089] The above resin curing device (530) may be provided in one or more ways to gradually increase the curing rate of the bonding resin (20r), and the resin curing device (530) may be configured to control the curing intensity or curing time of the bonding resin (20r).

[0090] Meanwhile, in the embodiment illustrated in FIG. 3, the resin dispenser (520), resin curing machine (530), and flattening cover die (400) are shown to be arranged sequentially from one side to the other, but this is merely an example, and the flattening cover die (400) may be arranged between the resin dispenser (520) and the resin curing machine (530), or a plurality of resin curing machines (530) may be arranged both before and after the flattening cover die (400).

[0091] A flattening cover die (400) is placed on the optical fiber supply line (510). The flattening cover die (400) stably supports a plurality of optical fibers (10) moving along the optical fiber supply line (510) and, at the same time, performs the function of flattening the surface of the bonding resin sprayed from the resin dispenser (520).

[0092] That is, the surface of the joint of a plurality of optical fibers (10) in a state where the bonding resin (20r) is sprayed or cured can be flattened by passing through the space between the lower cover die (410) and the upper cover die (420) constituting the flattening cover die (400).

[0093] FIG. 4 shows a cross-sectional view of a flattening cover die of an optical fiber ribbon joint flattening system according to the present invention.

[0094] FIG. 4(a) shows a cross-sectional view of the upper cover die, and FIG. 4(b) shows a cross-sectional view of the lower cover die.

[0095] As illustrated in FIG. 4, the flattening cover die (400) comprises: a lower cover die (410) positioned on the optical fiber supply line (510) to support a plurality of optical fibers (10) moving along the optical fiber supply line (510) from below; and an upper cover die (420) positioned above the lower cover die (410) in an upward and downward direction to flatten the surface of the junction between adjacent optical fibers forming a rollable optical fiber ribbon.

[0096] The lower cover die (410) and the upper cover die (420) constituting the flattening cover die (400) can be made of various materials such as steel, aluminum, alloy, ceramic, and plastic.

[0097] Additionally, the lower cover die (410) is formed with a larger cross-sectional area than the upper cover die (420), and the upper cover die (420) can be driven in an up-and-down direction to come into contact with or be separated from the lower cover die (410) by an external force on the lower cover die (410).

[0098] The lower cover die (410) is installed in a fixed position so that its relative position to the optical fiber supply line (510) is maintained at a constant level, and an optical fiber receiving groove (410h) may be formed in the central part of the lower cover die (410) to accommodate a plurality of optical fibers (10) in a seated state. The optical fiber receiving groove (410h) may be in the form of a plurality of grooves arranged in a continuous manner, and the grooves may be formed as curved surfaces such as hemispherical shapes or V-shaped angled planes.

[0099] The lower cover die (410) receives a plurality of optical fibers (10) in the optical fiber receiving groove (410h), stably supports the plurality of optical fibers (10) supplied along the optical fiber supply line (510), and prevents the position of the plurality of optical fibers (10) arranged in a row from shifting while the surface of the bonding resin (10r) is flattened.

[0100] In addition, the lower cover die (410) can maintain the position of a plurality of optical fibers (10) received in the optical fiber receiving groove (410h) so that the spraying and curing process of the bonding resin (20r) can be performed.

[0101] The upper cover die (420) is positioned on the top of the lower cover die (410), and the upper cover die (420) and the lower cover die (410) can be designed to face each other in the vertical direction.

[0102] The upper cover die (420) has an optical fiber cover groove (420h) formed therein that covers the upper region of a plurality of optical fibers (10) received in the optical fiber receiving groove (410h) of the lower cover die (410).

[0103] At this time, the optical fiber cover groove (420h) of the upper cover die (420) and the optical fiber receiving groove (410h) of the lower cover die (410) are configured with cross-sectional widths (w) that correspond to each other, and the inner surface of the optical fiber cover groove (420h) of the upper cover die (420) facing the optical fiber receiving groove (410h) of the lower cover die (410) can be configured to be flat.

[0104] FIG. 5 illustrates a cross-sectional view of a state in which the surface of a joint is flattened through a flattening cover die constituting a fiber optic ribbon joint flattening system according to the present invention.

[0105] As shown in FIGS. 4 and 5, when the upper cover die (420) and the lower cover die (410) are assembled to face each other, a void space can be formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h) through which a plurality of optical fibers (10) with bonding resin (20r) applied can pass.

[0106] While a plurality of optical fibers (10) received in the optical fiber receiving groove (410h) of the lower cover die (410) are moving along the optical fiber supply line (510), the surface of the bonding resin (20r) can be flattened as the plurality of optical fibers (10) pass through the empty space formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h).

[0107] Specifically, the bonding resin (20r) sprayed or cured in the boundary area of ​​the optical fiber (10) initially has an upwardly convex shape, but as it passes through the empty space formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h), the bonding resin (20r) applied to the boundary area of ​​the optical fiber (10) is pressed or spread by the inner surface of the optical fiber cover groove (420h) of the upper cover die (420), so that the surface of the bonding resin (20r) can be flattened.

[0108] With the lower cover die (410) and the upper cover die (420) facing each other, the groove height (t), which is the maximum height of the empty space formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h), can be formed to be slightly larger than the outer diameter of the optical fiber (10). If the groove height (t) is made equal to the outer diameter of the optical fiber (10), surface damage to the optical fiber may occur during the joint flattening process, so it is preferable to configure the groove height (t) to be larger than the outer diameter of the optical fiber (10).

[0109] As a result, when a plurality of optical fibers (10) pass through the empty space formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h), the surface of the bonding resin (20r) is flattened, and the total height of the rollable optical fiber ribbon including the bond formed on the surface of the optical fiber (10) can be flattened so as not to exceed the groove height (t).

[0110] Here, when the surface of the joint is flattened with an excessive amount of bonding resin (20r) applied between a pair of optical fibers (10) at the location where the joint (20) is to be formed, some of the bonding resin may be pushed in the width direction through the empty space formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h) and move toward the adjacent optical fiber (10) where the joint (20) should not be formed.

[0111] In this case, the bonding area between one or more of the pair of optical fibers (10) at the location where the bonding portion (20) is to be formed and the bonding resin (20r) is excessively increased by the bonding resin (20r) that is moved in the width direction, and the separation strength is increased, so the surface of the optical fiber (10) may be torn and damaged during the process of separating the optical fiber (10) from the rollable optical fiber ribbon (100). In addition, if the bonding resin (20r) is moved excessively, the bonding portion (20) may be unintentionally formed between the pair of optical fibers at a location where the bonding portion (20) should not be formed, so the shape of the rollable optical fiber ribbon (100) cannot be maintained and the rolling flexibility in the width direction may also be reduced.

[0112] The bonding resin (20r), whose surface is flattened by passing through the empty space formed between the optical fiber cover groove (420h) and the optical fiber receiving groove (410h), is subsequently cured by passing through a resin curing machine (530), thereby finally being completed as a bonding part of a rollable optical fiber ribbon with excellent durability and strength.

[0113] Furthermore, the present invention can provide a rollable optical fiber ribbon (100) manufactured through the aforementioned optical fiber ribbon joint flattening system (1000).

[0114] FIG. 6 illustrates a plan view of a rollable optical fiber ribbon constituting an optical cable according to the present invention.

[0115] A rollable optical fiber ribbon (100) constituting an optical cable according to the present invention comprises an optical fiber assembly in which a plurality of optical fibers (10) are arranged in parallel, and a plurality of joints (20) each intermittently arranged along the optical fiber length direction between an adjacent pair of optical fibers (10) among the plurality of optical fibers (10) included in the optical fiber assembly.

[0116] Here, the optical fiber assembly may be composed of a single-layer optical fiber assembly in which a plurality of optical fibers (10) are arranged side by side in a single layer, or a multilayer optical fiber assembly in which such single-layer optical fiber assemblies are stacked in multiple layers. If the optical fiber assembly has a multilayer structure, it can be used to construct a high-capacity optical communication network in a form that allows for batch connection.

[0117] In the above-described rollable optical fiber ribbon (100), an adjacent pair of optical fibers (10) among a plurality of optical fibers (10) are joined at the junction (20) intermittently arranged along the optical fiber length direction, and the remaining non-joined area excluding the junction (20) is maintained in a non-joined state, allowing rolling in the width direction. Therefore, the rollable optical fiber ribbon (100) can be efficiently accommodated in the internal space of the optical cable.

[0118] In this way, each optical fiber (10) constituting the rollable optical fiber ribbon (100) must maintain a mutually bonded state with sufficient bonding force at the bonding portion (20), but during branching operations, the bonded pair of optical fibers (10) need to be easily separated from each other.

[0119] Specifically, when separating the optical fibers (10), the operator can separate the joined optical fibers (10) by pulling them in the width direction of the ribbon, which is perpendicular to the length direction. At this time, the separation force required to separate the pair of optical fibers (10) in the vertical direction opposite to the length direction so that the pair of optical fibers (10) separated at each joint (20) become a 'T' shape overall is called the vertical separation force (T-peel force, hereinafter 'T').

[0120] Here, the vertical separation strength (T) is measured during the process of separating the pair of optical fibers (10) by pulling the fixed ends of the pair of optical fibers (10) in opposite directions at a preset speed, after fixing each end of the pair of optical fibers (10) joined through any plurality of consecutive joints (20) in the optical fiber length direction of the rollable optical fiber ribbon (100) to a separation strength measuring device.

[0121] FIG. 7 illustrates a vertical separation strength measuring device for measuring vertical separation strength at a joint of a rollable optical fiber ribbon constituting an optical cable according to the present invention.

[0122] FIG. 7 shows the measurement of vertical separation strength (T) at each joint (20) of a rollable optical fiber ribbon (100) constituting an optical cable according to the present invention. To measure the vertical separation strength (T), the ends of a pair of optical fibers (10) joined by mutually spaced joints (20) of the rollable optical fiber ribbon (100) are branched, and then each end of the branched pair of optical fibers (10) is fixed to each grip (1200) provided on a pair of mounts (1100) that are movable in the opposite direction of the vertical separation strength measuring device (1000). Then, the separation strength at each joint (20) is measured during the process of separating the pair of optical fibers (10) by pulling each optical fiber of the pair of optical fibers (10) fixed to the pair of grips (1200) in the opposite direction at a speed of about 500 mm / min.

[0123] Specifically, the separation strength test device (1000) measured the magnitude of the separation force required to separate one joint (20), that is, the vertical separation strength (T) at one joint (20), using a sensor such as a load cell during the process in which a pair of joined optical fibers (10) constituting a rollable optical fiber ribbon (100) split and separate in a vertical direction.

[0124] Here, the vertical separation strength is determined as the minimum value of the peak section among the values ​​measured at four consecutively arranged joints (20) in the longitudinal direction between a pair of joined optical fibers (10) extracted from the rollable optical fiber ribbon (100) to be measured.

[0125] [Table 1] below is an experimental example showing the results of extracting 11 optical fiber pair specimens containing 5 joints (20) arranged in a continuous parallel along the optical fiber length direction from a rollable optical fiber ribbon (100) containing 12 optical fibers having an outer diameter of 250 μm, measuring the cross-sectional area perimeter of one joint (20) at the end, and then measuring the vertical separation strength (T) of the remaining 4 joints (20) respectively.

[0126] Figure 8 illustrates the extraction of a rollable optical fiber ribbon specimen and a plurality of optical fiber pair specimens from a rollable optical fiber ribbon.

[0127] Referring to FIG. 8, the 11 optical fiber pair specimens (300) comprise five joints (20) arranged continuously along the length of the optical fiber (10) in a rollable optical fiber ribbon (100), and are extracted from two rollable optical fiber ribbon specimens (200(1), 200(2)) cut at a position spaced 10 cm apart from the first joint. From one of the two rollable optical fiber ribbon specimens (200(1), 200(2)), the odd-numbered Six pairs of optical fibers including a junction (20(1,1),20(1,2),20(1,3),20(1,4),20(1,5),20(3,1),20(3,2),20(3,3),20(3,4),20(3,5),20(5,1),20(5,2),20(5,3),20(5,4),20(5,5),20(7,1),20(7,2),20(7,3),20(7,4),20(7,5),20(9,1),20(9,2),20(9,3),20(9,4),20(9,5),20(11,1),20(11,2),20(11,3),20(11,4),20(11,5)). A specimen (300(1), 300(3), 300(5), 300(7), 300(9), 300(11)) is extracted, and each even-numbered from another rollable optical fiber ribbon specimen (200(2)) Five optical fiber pair specimens (300(2), 300(4), 300(6), 300(8), 300(10)) including a joint (20(2,1), 20(2,2), 20(2,3), 20(2,4), 20(2,5), 20(4,1), 20(4,2), 20(4,3), 20(4,4), 20(4,5), 20(6,1), 20(6,2), 20(6,3), 20(6,4), 20(6,5), 20(8,1), 20(8,2), 20(8,3), 20(8,4), 20(8,5), 20(10,1), 20(10,2), 20(10,3), 20(10,4), 20(10,5)) are extracted.

[0128] Here, the extraction method of the rollable optical fiber ribbon specimen (200) containing N optical fibers and the (N-1) optical fiber pair specimens (300) may be changed according to the arrangement pattern of the joint (20) forming the rollable optical fiber ribbon (100).

[0129] Additionally, while it is most preferable to evaluate the cross-sectional area perimeter and vertical separation strength (T) of the junction (20) on the same optical fiber pair specimen (300), they may also be measured from separate optical fiber pair specimens (300), and in such cases, it is preferable to extract the separate optical fiber pairs (300) from areas that are placed as close as possible in the longitudinal direction of the optical fiber (10).

[0130] In the experimental example below, the cross-sectional perimeter of the terminal joint (20(1,5)) among the five consecutively arranged joints (20(1,1), 20(1,2), 20(1,3), 20(1,4), 20(1,5)) that join the first optical fiber (10(1)) and the second optical fiber (10(2)) constituting the rollable optical fiber ribbon (100) was measured, and the vertical separation strength (T) of each of the remaining four joints (20(1,1), 20(1,2), 20(1,3), 20(1,4)) was measured in the order of the joints that separate first. Likewise, the cross-sectional perimeter of the terminal joint (20(11,5)) among the five consecutive joints (20(11,1), 20(11,2), 20(11,3), 20(11,4), 20(11,5)) joining the eleventh optical fiber (10(11)) and the twelfth optical fiber (10(12)) was measured, and the vertical separation strength (T) of each of the remaining four joints (20(11,1), 20(11,2), 20(11,3), 20(11,4)) was measured.

[0131] For a total of 11 optical fiber pair specimens (300), the vertical separation strength (T) was measured in the same manner, and from the measured values ​​of the vertical separation strength (T), the sample standard deviation (σl) of the vertical separation strength (T) of the four joints (20) arranged continuously in the longitudinal direction of each optical fiber pair specimen (300) and the sample standard deviation (σw) of the vertical separation strength (T) of the joints (20) arranged in the width direction of all optical fiber pair specimens (300) were calculated.

[0132] In [Table 1] below, Comparative Example 1 is a measurement of the vertical separation strength (T) from each joint (20) of a plurality of optical fiber pair specimens (300) extracted from a rollable optical fiber ribbon specimen (200) in which each joint (20) of the rollable optical fiber ribbon (100) has not undergone a joint surface flattening process through a flattening cover die (400, see FIG. 3). Comparative Example 2 is a measurement of the vertical separation strength (T) from each joint (20) of a plurality of optical fiber pair specimens (300) extracted from a rollable optical fiber ribbon specimen (200) in which each joint (20) of the rollable optical fiber ribbon (100) has undergone a joint surface flattening process through a flattening cover die (400), but the joint (20) is formed with an insufficient amount of bonding resin (20r). Comparative Example 3 is a vertical separation strength (T) measured from each joint (20) of a plurality of optical fiber pair specimens (300) extracted from a rollable optical fiber ribbon specimen (200) in which each joint (20) of a rollable optical fiber ribbon (100) underwent a joint surface flattening process through a flattening cover die (400) but the joint (20) was formed with an excessive amount of bonding resin (20r).

[0133] In [Table 2] below, Examples 1 and 2 measure the vertical separation strength (T) from each joint (20) of a plurality of optical fiber pair specimens (300) extracted from a rollable optical fiber ribbon specimen (200) in which the surface of each joint (20) is flattened while the amount of bonding resin (20r) is appropriately applied.

[0134] When the vertical separation strength (T) of each joint (20) of the rollable optical fiber ribbon (100) is between 2gf and 10gf, it can provide appropriate bonding strength. That is, if the vertical separation strength (T) value is less than 2gf, the bonding strength between the optical fibers (10) is insufficient, so the optical fibers are easily separated from each other, and the structure of the rollable optical fiber ribbon (100) cannot be maintained against stress applied during the cable manufacturing and installation process, etc., and if the vertical separation strength (T) value is greater than 10gf, the bonding strength between the optical fibers (10) increases excessively, making it difficult for a worker to handle during the optical fiber separation process, and damage to the optical fibers (10), such as the surface of the optical fibers being torn, may occur.

[0135] In addition, the longitudinal standard deviation (σ) calculated from the vertical separation strength (T) measured at each joint (20) of the rollable optical fiber ribbon specimen (200) in the example l ) and width direction standard deviation (σ w A uniform bonding strength can be provided when each of ) is within 2.0, preferably 1.0 or less.

[0136] Vertical separation strength [gf] Cross-sectional area Perimeter [μm] Lengthwise joint 1 Lengthwise joint 2 Lengthwise joint 3 Lengthwise joint 4 Lengthwise standard deviation (σ l)Longitudinal Joint 5 Comparison Example 1 Fiber optic pair specimen 12.5 4.49.8 10.03.8 0 10 5 3 Fiber optic pair specimen 27.07.49.16.61.08 10 2 3 Fiber optic pair specimen 32.69.02.72.63.18 9 9 8 Fiber optic pair specimen 45.57.35.92.91.85 11 9 5 Fiber optic pair specimen 52.96.45.64.51.53 9 5 4 Fiber optic pair specimen 64.64.36.03.31.1 1 7 8 5 Fiber optic pair specimen 73.14.8 1.62.51.35 7 2 6 Fiber optic pair specimen 83.53.79.69.43.41 12 2 5 Fiber optic pair specimen 97.07.06.08.10.871159 Fiber optic pair specimen 105.72.43.19.03.011035 Fiber optic pair specimen 116.76.12.82.92.04903 Standard deviation in width direction (σ w )2.222.062.552.80 Comparison Example 2 Fiber Optic Pair Specimen 17.02.87.45.72.06444 Fiber Optic Pair Specimen 23.33.64.37.61.97383 Fiber Optic Pair Specimen 36.72.06.72.52.56496 Fiber Optic Pair Specimen 41.96.21.74.02.09579 Fiber Optic Pair Specimen 56.96.37.85.11.13528 Fiber Optic Pair Specimen 67.87.02.95.02.20558 Fiber Optic Pair Specimen 72.71.72.87.12.39580 Fiber Optic Pair Specimen 86.71.64.76.72.41492 Fiber Optic Pair Specimen 92.4 2.7 3.15 81.5 7394 Fiber optic pair specimen 102.9 7.12.7 7.5 2.6 0407 Fiber optic pair specimen 111.17 12.16 83.12 367 Standard deviation in width direction (σ w)2.50 2.34 2.18 1.57 Comparison Example 3 Fiber optic pair specimen 19.8 11.1 11.38.5 1.32 1470 Fiber optic pair specimen 29.6 10.37.6 7.11.57 1518 Fiber optic pair specimen 38.17.1 10.98.31.60 1885 Fiber optic pair specimen 49.9 10.8 8.09.7 1.16 1604 Fiber optic pair specimen 57.5 10.7 10.8 11.01.65 1868 Fiber optic pair specimen 69.49.39.1 11.20.95 1555 Fiber optic pair specimen 78.5 10.48.9 10.00.90 1941 Fiber optic pair specimen 89.78.08.07.31.04 1767 Fiber optic pair specimen 97.37.08.411.42.001553 Fiber optic pair specimen 109.97.210.77.41.781573 Fiber optic pair specimen 1110.210.610.37.61.381805 Standard deviation in width direction (σ w )1.031.661.361.68

[0137] Vertical separation strength [gf] Cross-sectional area Perimeter [μm] Lengthwise joint 1 Lengthwise joint 2 Lengthwise joint 3 Lengthwise joint 4 Lengthwise standard deviation (σ l )Longitudinal joint 5 Example 1 Optical fiber pair specimen 18.37.87.07.20.59690 Optical fiber pair specimen 27.17.55.45.81.04769 Optical fiber pair specimen 36.97.96.57.70.65700 Optical fiber pair specimen 46.46.27.36.30.49784 Optical fiber pair specimen 58.07.16.66.50.70720 Optical fiber pair specimen 67.65.97.85.31.24802 Optical fiber pair specimen 75.88.07.87.60.98775 Optical fiber pair specimen 85.35.75.67.20.87680 Optical fiber pair specimen 96.17.86.77.20.70831 Optical fiber pair specimen 105.07.86.86.61.14863 Optical fiber pair specimen 117.66.46.25.70.84868 Standard deviation in width direction (σ w)0.990.850.790.87 Example 2 Fiber optic pair specimen 16.615.305.416.280.651471 Fiber optic pair specimen 26.465.905.805.150.541307 Fiber optic pair specimen 37.456.617.827.650.531473 Fiber optic pair specimen 47.635.125.367.981.491285 Fiber optic pair specimen 55.556.087.317.000.811354 Fiber optic pair specimen 65.545.926.877.680.961435 Fiber optic pair specimen 76.227.685.846.880.811124 Fiber optic pair specimen 85.787.275.805.800.741352 Fiber optic pair specimen 97.826.397.396.250.771236 Fiber optic pair specimen 105.527.535.787.651.131237 Fiber optic pair specimen 115.626.217.775.900.961326 Standard deviation in width direction (σ w )0.890.850.970.93

[0138] Referring to Tables 1 and 2 above, Comparative Example 1 does not undergo a joint surface flattening process, so the longitudinal standard deviation (σ) between each joint (20) within the rollable optical fiber ribbon specimen (200) l ) and width direction standard deviation (σ w It was confirmed that ) is large and some joints (20) do not satisfy the vertical separation strength (T) criteria required in the present invention. Comparative Example 2 underwent a joint surface flattening process, but because the amount of bonding resin (20r) was insufficient, a substantial joint surface flattening effect was not obtained, and thus the longitudinal standard deviation (σ) between each joint (20) in the rollable optical fiber ribbon specimen (200) l ) and width direction standard deviation (σ wIt was confirmed that the vertical separation strength (T) was excessively low in multiple joints (20) and that Comparative Example 3 underwent a joint surface flattening process, but the amount of bonding resin (20r) was excessive, so it was confirmed that the vertical separation strength (T) was excessively high in multiple joints (20). On the other hand, in Examples 1 and 2, by flattening the surface of the joints (20) formed with an appropriate amount of bonding resin (20r) using a flattening cover die (300), multiple joints (20) included in the rollable optical fiber ribbon (100) were uniformly formed in the length and width directions with appropriate bonding strength. Through this, it was confirmed that the problem of the optical fiber (10) being unintentionally separated from the rollable optical fiber ribbon (100) can be prevented, and damage to the optical fiber (10) can be prevented even during the separation process of the optical fiber (10). FIGS. 9 to 15 illustrate cross-sectional views showing enlarged views of various embodiments of the optical fiber and the joint portion constituting the rollable optical fiber ribbon constituting the optical cable according to the present invention in the AA' cross-section of FIG. 6.

[0139] Referring to FIG. 9, if we examine the cross-sectional structure of the optical fiber (10) constituting the rollable optical fiber ribbon (100), the optical fiber (10) may be configured to include a core (11), a clad layer (12), a coating layer (13), and a coloring layer (14).

[0140] The core (11) may be composed of glass or synthetic resin and transmits light. The clad layer (12) may be formed to surround the core (11).

[0141] The above clad layer (12) uses a silica material, such as glass or synthetic resin, with a relatively lower refractive index than the core (11), thereby causing total internal reflection of light passing through the center of the optical fiber to perform the function of transmitting a signal.

[0142] The coating layer (13) may be formed by coating the surface of the clad layer (12) with a material comprising at least one of acrylate, polyimide, and carbon. The coating layer (13) is configured to directly surround the clad layer (12) and performs the function of absorbing external shocks transmitted to the clad layer (12). The coating layer (13) may be composed of multiple layers with different physical properties, such as modulus, to safely protect internal components.

[0143] The coloring layer (14) is formed by applying a material containing a coloring agent, such as a colored or colorless pigment, to the surface of the coating layer (13) to impart color to the optical fiber (10), thereby enabling mutual identification with other optical fibers through color. Each optical fiber (10) constituting the rollable optical fiber ribbon (100) may have a coloring layer (14) on its outermost surface to enable mutual identification between the optical fibers (10).

[0144] Each joint (20) constituting the rollable optical fiber ribbon (100) that constitutes the optical cable according to the present invention is positioned in the boundary region between an adjacent pair of optical fibers (10) among a plurality of optical fibers (10) joined side by side, and the surface of the joint (20) may be configured in a flat shape.

[0145] In the embodiment illustrated in FIG. 9, the joint (20) is shown as having a flat surface top, but this is merely an example, and in reality, the joint (20) may have a shape where only a portion of the surface is pressed and only a portion of the surface top is flattened.

[0146] The above-mentioned joint (20) is formed to wrap relatively uniformly around the outer circumference of each optical fiber (10) joined through the joint, and thus the contact area between the optical fiber (10) and the joint (20) is maintained so that it is neither excessive nor insufficient, thereby ensuring a consistent connection between the optical fiber (10) and the joint (20).

[0147] Meanwhile, unlike a general optical fiber ribbon having a joint formed by continuously wrapping the optical fiber along the optical fiber length direction, a rollable optical fiber ribbon (100) having a joint (20) intermittently arranged along the optical fiber length direction has a relatively small joint area between the optical fiber (10) and the joint (20). As a result, in order to prevent unwanted separation between the optical fiber (10) and the joint (20), a sufficient bonding force is required in the relatively small joint area between the optical fiber and the joint.

[0148] Each optical fiber (10) constituting the rollable optical fiber ribbon (100) that constitutes the optical cable according to the present invention must maintain a mutually bonded state with the bonding portion (20) by sufficient bonding force, and at the same time, when a pair of bonded optical fibers (10) must be separated during the connection process of the rollable optical fiber ribbon (100), the coloring layer (14) placed on the surface of the optical fiber (10) must not be damaged.

[0149] Meanwhile, when manufacturing the optical fiber, the coloring layer (14) of the optical fiber (10) is formed through a coloring process that imparts color to the surface of the optical fiber (10) in a process atmosphere containing oxygen (O2) and nitrogen (N2) having a preset concentration ratio. In this process, the coloring layer (14) may be exposed to the process atmosphere and contain a certain concentration of oxygen (O2).

[0150] Here, if the concentration of oxygen (O2) contained in the process atmosphere increases, the adhesion strength of the coloring layer (14) to the coating layer (13) decreases, which may cause the coloring layer (14) to not adhere properly to the surface of the optical fiber (10) or to easily separate from the coating layer (13). Therefore, in order to provide sufficient adhesion strength between the coloring layer (14) and the coating layer (13), it is desirable to control the concentration of oxygen (O2) contained in the process atmosphere during the coloring process to a level below a certain level.

[0151] However, in the above coloring process, the oxygen (O2) concentration contained in the process atmosphere has a characteristic that is proportional to the bonding strength between the optical fiber (10) and the junction (20). That is, if the bonding strength of the coloring layer (14) is improved by lowering the oxygen concentration, there exists a trade-off relationship in which the bonding strength between the optical fiber (10) and the junction (20) is simultaneously reduced.

[0152] In the above coloring process, it is desirable that the oxygen (O2) concentration contained in the process atmosphere be controlled to 300 ppm or less.

[0153] In order to compensate for the reduction in bonding strength between the optical fiber (10) and the bonding part (20) while maintaining a low oxygen (O2) concentration in the process atmosphere during the coloring process, the ratio of the cross-sectional area of ​​the bonding part (20) to the circumference of one of the pair of optical fibers (10) bonded through the bonding part (20) in a cross-section cut perpendicular to the optical fiber length direction is configured to be in the range of 47% to 84%, thereby effectively maintaining the bonding strength between the coloring layer (14) and the bonding part (20).

[0154] The outer diameter of each optical fiber (10) constituting the rollable optical fiber ribbon (100) may be in the range of 160 micrometers to 260 micrometers (μm), and the circumference of the optical fiber (10) may be calculated by multiplying the outer diameter (μm) of the optical fiber (10) by pi (π).

[0155] And the cross-sectional area perimeter of the joint (20) formed in the boundary region between a pair of optical fibers (10) in the rollable optical fiber ribbon (100) can be calculated using the following [Equation 1].

[0156] [Equation 1]

[0157] Cross-sectional area of ​​the joint = Length (ℓ1) of the inner surface (21) where the joint contacts the outer circumference of one optical fiber + Length (ℓ2) of the inner surface (22) where the joint contacts the outer circumference of another optical fiber + Length (ℓ3) of the outer surface (23) where the joint does not contact the optical fiber

[0158] If the ratio of the cross-sectional circumference of the joint (20) to the circumference of the optical fiber (10) is less than 47%, the bonding force between the joint (20) and the optical fiber (10) in the area between a pair of optical fibers (10) may be insufficient.

[0159] On the other hand, if the ratio of the cross-sectional circumference of the joint (20) to the circumference of the optical fiber (10) exceeds 84%, as shown in FIG. 10, the cross-sectional area of ​​the joint (20) becomes excessively large, and the joint (20x) may be unnecessarily formed by encroaching upon the area of ​​an adjacent optical fiber (10) in an unintended non-joined state, rather than the adjacent pair of optical fibers (10) where the joint is intentionally placed. As a result, a joint different from the intended joint pattern to provide sufficient flexibility is formed, making it difficult for the rollable optical fiber ribbon (100) to roll smoothly in the width direction. Additionally, if the area of ​​the joint (20) in contact with the optical fiber (10) becomes excessively large, excessive stress may be applied to the optical fiber (10) when a pair of strongly joined optical fibers (10) are vertically separated, or the outermost layer of the optical fiber (10), such as the coloring layer (14), may be torn or damaged.

[0160] In this way, the rollable optical fiber ribbon (100) constituting the optical cable according to the present invention can provide excellent bonding strength between the optical fiber (10) and the bonding part (20) and prevent damage or tearing of the coloring layer (14) by optimizing the ratio of the cross-sectional area of ​​the bonding part (20) to the circumference of the optical fiber (10) to a range of 47% to 84%, even if the concentration of oxygen (O2) contained in the coloring layer (14) of the optical fiber (10) is controlled to be low at 300 ppm or less.

[0161] Each joint (20) constituting the rollable optical fiber ribbon (100) that constitutes the optical cable according to the present invention includes an inner surface (21, 22) that is in direct contact with the optical fiber (10) and an outer surface (23) that is not in direct contact with the optical fiber. The outer surface (23) of the cross section of the joint (20) may be formed flat overall as shown in FIG. 9, but may also be formed in a curved shape having a radius of curvature on at least some surface as shown in FIG. 11.

[0162] The outer surface (23) of the joint (20) formed in the above curve shape may, more specifically, include a smooth portion (23f) flattened by the flattening cover die (400) and two connecting portions (23c, 23c') disposed on one or both sides of the smooth portion (23f) and connected to each end of the inner surface (21, 22).

[0163] Here, the smooth portion (23f) and the two connecting portions (23c, 23c') may each be flat or curved, and if they are curved, the radius of curvature (Rf) of the smooth portion (23f) may be larger than the radius of curvature (Rc) of the connecting portions (23c, 23c'). In this case, when separating the optical fiber (10) from the rollable optical fiber ribbon (100), the separation from the optical fiber (10) begins from the connecting portion (20) side rather than the smooth portion (23f) side, thereby providing robust and uniform bonding characteristics and stably maintaining the structure of the rollable optical fiber ribbon (100).

[0164] In addition, the rollable optical fiber ribbon (100) constituting the optical cable according to the present invention can appropriately press the bonding resin (20r) using a flattening cover die (400) to secure the length (ℓ1,ℓ2) of the inner surface (21, 22) where the bonding portion (20) sufficiently contacts the outer circumference of a pair of adjacent optical fibers (10a, 10b). At this time, the degree of pressure applied to the bonding resin (20r) through the flattening cover die (400) can be controlled through the surface roughness of the smooth portion (23f) formed on the outer surface (23) of the bonding portion (20).

[0165] Here, the surface roughness of the smooth portion (23f) is the arithmetic average roughness (R) of the JIS B0601 standard. a It means ).

[0166] Preferably, the arithmetic mean roughness (R) of the smooth portion (23f) formed on the outer surface (23) of the joint portion (20) of the rollable optical fiber ribbon (100) constituting the optical cable according to the present invention a ) can be composed of 2 micrometers (μm) or less.

[0167] The arithmetic mean roughness (R) of the smooth portion (23f) formed on the outer surface (23) of the joint portion (20) a ) can be measured using a shape measuring laser microscope (VK-X100) from KEYENCE in accordance with the JIS B0601 standard.

[0168] If, the arithmetic mean roughness (R) of the smooth portion (23f) a If the length (ℓ1,ℓ2) of the inner surface (21, 22) that contacts the outer circumference of an adjacent pair of optical fibers (10a, 10b) is not sufficiently secured, and as a result, a bonding strength is reduced, and it may be difficult to maintain a stable bonding state between the optical fiber (10) and the bonding part (20).

[0169] In addition, the rollable optical fiber ribbon (100) constituting the optical cable according to the present invention can adjust the degree of pressure applied to the bonding resin (20r) through the flattening cover die (400) in order to secure the length (ℓ1,ℓ2) of the inner surface (21,22) where the bonding portion (20) sufficiently contacts the outer circumference of an adjacent pair of optical fibers (10a, 10b). At this time, the degree of pressure can be controlled through the height difference between the highest point and the lowest point of the bonding portion (20) and a reference line (L), which is a straight line connected by simultaneously contacting each outer circumference of an adjacent pair of optical fibers (10a, 10b) at the cross-section of the optical fiber ribbon (100).

[0170] As shown in FIGS. 12 and 13, the height difference (H) from the highest point of the joint (20) relative to the reference line (L) UP ) is 30 micrometers (μm) or less, and the height difference (H) with the lowest point of the joint (20) DN ) can also be composed of 30 micrometers (μm) or less.

[0171] The height difference (H) between the reference line (L) and the highest point of the joint (20) UP If the length exceeds 30 micrometers (μm), the bonding resin (20r) is not sufficiently pressed through the flattening cover die (400), so the length of the inner surface (21, 22) where the bonding part (20) contacts the outer circumference of each optical fiber (10a, 10b) cannot be sufficiently secured. As a result, the vertical separation strength between the optical fiber (10) and the bonding part (20) is lowered, which may cause unwanted separation of the optical fibers, and this may cause difficulty in maintaining the shape of the optical fiber ribbon.

[0172] In addition, the height difference (H) between the reference line (L) and the lowest point of the joint (20) DNIf the length exceeds 30 micrometers (μm), the amount of bonding resin (20r) pressed by the flattening cover die (400) is insufficient, and as a result, the length of the inner surface (21, 22) that the bonding part (20) contacts with the outer circumference of each optical fiber (10a, 10b) cannot be sufficiently secured, so a substantial pressing effect cannot be obtained.

[0173] In addition, the rollable optical fiber ribbon (100) constituting the optical cable according to the present invention can adjust the degree of pressure applied to the bonding resin (20r) through the flattening cover die (400) in order to secure the length (ℓ1,ℓ2) of the inner surface (21, 22) where the bonding portion (20) sufficiently contacts the outer circumference of a pair of adjacent optical fibers (10a, 10b). At this time, the degree of pressure can be controlled through the angle (θ1, θ2) formed by the line connecting the end of each connecting portion (23c, 23c') formed on the outer surface (23) of the bonding portion (20) to the center of the optical fiber, and the line connecting the center of each optical fiber (10a, 10b) perpendicularly to the reference line (L).

[0174] As shown in FIGS. 14 and 15, the angle (θ1, θ2) formed by the line connecting the end of each connection part (23c, 23c') formed on the outer surface (23) of the joint (20) to the center of the optical fiber, and the line connecting the center of each optical fiber (10a, 10b) perpendicularly to the reference line (L), can be configured in the range of -30 degrees (˚) to -1 degree (˚) or 1 degree (˚) to 40 degrees (˚).

[0175] Here, based on the line connecting the end of each connection part (23c, 23c') and the center of the optical fiber perpendicularly to the reference line (L) at the center of each optical fiber (10a, 10b), the case where the line connecting the end of each connection part (23c, 23c') and the center of the optical fiber forms the direction of the junction part (20) is defined as the negative (-) direction, and the case where it forms the opposite direction of the junction part is defined as the positive (+) direction.

[0176] Referring to FIG. 14, if the angle (θ1, θ2) formed by the line connecting the end of each connecting part (23c, 23c') of the joint (20) and the center of the optical fiber, and the line connecting the center of each optical fiber (10a, 10b) perpendicularly to the reference line (L), is less than -30 degrees (˚), the length (ℓ1, ℓ2) of the inner surface (21, 22) where the outer circumference of each optical fiber (10a, 10b) contacts the joint (20) is insufficient, and as a result, the vertical separation strength between the optical fiber (10) and the joint (20) is low, causing an unwanted separation of the optical fiber, which may make it difficult to maintain the shape of the optical fiber ribbon.

[0177] Additionally, referring to FIG. 15, if the angle (θ1, θ2) formed by the line connecting the end of each connecting part (23c, 23c') of the joint (20) and the center of the optical fiber, and the line connecting each optical fiber (10a, 10b) perpendicularly to the reference line (L), exceeds 40 degrees (˚), the length (ℓ1, ℓ2) of the inner surface (21, 22) where the joint (20) and the outer circumference of each optical fiber (10a, 10b) come into contact becomes excessively long, and the vertical separation strength may increase significantly. As a result, when separating the optical fiber from the optical fiber ribbon, the risk of damage to the optical fiber increases, such as the outermost layer of the optical fiber (10) being damaged, and as shown in FIG. 10, the bonding resin may encroach upon unintended non-bonding areas, thereby forming unnecessary joints (20x).

[0178] Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art may modify and change the present invention in various ways without departing from the spirit and scope of the present invention as described in the claims below. Therefore, if a modified embodiment basically includes the components of the claims of the present invention, it should be considered to be included within the technical scope of the present invention.

Claims

1. An optical cable core comprising a plurality of optical fiber ribbons; and, Includes a cable jacket wrapping the optical cable core; The optical fiber ribbon comprises: an optical fiber assembly in which a plurality of optical fibers are arranged side by side, each optical fiber comprising a core, a clad layer surrounding the core, and one or more coating layers surrounding the clad layer; and a plurality of junctions intermittently arranged along the longitudinal direction between an adjacent pair of optical fibers among the plurality of optical fibers included in the optical fiber assembly. An optical cable characterized in that, in a cross-section perpendicular to the longitudinal direction of the optical fiber assembly, the outer surface that does not come into direct contact with the optical fiber of the junction includes a flattened portion.

2. In Paragraph 1, An optical cable characterized in that the highest point of the above-mentioned joint is positioned above a connected straight reference line while simultaneously contacting the outer surfaces of each of the pair of optical fibers on both sides of the joint.

3. In Paragraph 1, An optical cable characterized in that the outer surface of the above-mentioned joint includes a curved shape.

4. In Paragraph 1, An optical cable characterized in that the outer surface of the joint comprises a smooth portion and two connecting portions respectively disposed on both sides of the smooth portion.

5. In Paragraph 4, An optical cable characterized in that the radius of curvature of the smooth portion of the joint is larger than the radius of curvature of the connection portion.

6. In Paragraph 1, An optical cable characterized in that the above-mentioned joint is positioned to surround at least a portion of the circumference of each of the optical fibers joined through the joint in the region between an adjacent pair of optical fibers.

7. In Paragraph 6, An optical cable characterized in that, in a cross-section perpendicular to the longitudinal direction of the optical fiber, the ratio of the perimeter of the cross-sectional area of ​​the junction according to the following [Equation 1] to the circumference of any one of the pair of optical fibers joined by the junction is in the range of 47% to 84%. [Equation 1] Cross-sectional area of ​​the junction = Length of the inner surface where the junction contacts the outer circumference of one optical fiber (ℓ1) + Length of the inner surface where the junction contacts the outer circumference of another optical fiber (ℓ2) + Length of the outer surface of the portion where the junction does not contact the optical fiber (ℓ3) 8. In Paragraph 1, An optical cable characterized in that the vertical separation strength of the junction disposed between the optical fiber pairs provided in the optical fiber ribbon is 2gf to 10gf.

9. In Paragraph 8, The longitudinal standard deviation (σ) of the vertical separation strength of a plurality of junctions spaced longitudinally between optical fiber pairs provided in the optical fiber ribbon. l An optical cable characterized by ) being 2.0 or less, preferably 1.0 or less.

10. In Paragraph 8, The width-direction standard deviation (σ) of the vertical separation strength of the junctions respectively disposed between the plurality of optical fiber pairs provided in the optical fiber ribbon. l An optical cable characterized by ) being 2.0 or less, preferably 1.0 or less.

11. In Paragraph 4, Arithmetic Average Roughness (R) of the smooth portion formed on the outer surface of the above-mentioned joint according to JIS B0601 standard a An optical cable characterized by having a diameter of 2 micrometers (μm) or less.

12. In Paragraph 1, The height difference (H) from the highest point of the junction based on a straight reference line (L) connected by simultaneously contacting each outer surface of a pair of optical fibers on both sides of the junction. UP An optical cable characterized by having a diameter of 5 micrometers (μm) to 30 micrometers (μm).

13. In Paragraph 1, The height difference (H) from the lowest point of the junction based on a straight reference line (L) connected by simultaneously contacting the outer surfaces of each of the pair of optical fibers on both sides of the junction. DN An optical cable characterized by having a diameter of 5 micrometers (μm) to 30 micrometers (μm).

14. In Paragraph 1, An optical cable characterized in that the angle formed by a line connecting the end of each connection formed on the outer surface of the above-mentioned joint and the center of the optical fiber, and a line perpendicularly connected to a straight reference line that simultaneously contacts the outer surface of each pair of optical fibers on both sides of the above-mentioned joint at the center of each optical fiber, is in the range of -30 degrees (˚) to -1 degree (˚).

15. In Paragraph 1, An optical cable characterized in that the angle formed by a line connecting the end of each connection formed on the outer surface of the junction and the center of the optical fiber, and a line perpendicularly connected to a straight reference line that simultaneously contacts the outer circumference of each pair of optical fibers on both sides of the junction from the center of each optical fiber, is in the range of 1 degree (˚) to 40 degrees (˚).

16. An optical fiber supply line that supplies a plurality of optical fibers constituting an optical fiber ribbon in a predetermined direction while the plurality of optical fibers are arranged parallel to each other along the length direction; A resin dispenser disposed in the upper region of the optical fiber supply line and spraying bonding resin toward the optical fiber boundary region toward the optical fiber supply line; A flattening cover die disposed in the optical fiber supply line to flatten the surface of the bonding resin; and A fiber optic ribbon joint flattening system characterized by including a resin curing machine positioned in the upper region of the fiber optic supply line to cure the sprayed bonding resin.

17. In Paragraph 16, The above flattening cover die is, A lower cover die that supports a plurality of optical fibers from below, positioned on the optical fiber supply line and moving along the optical fiber supply line; and A fiber optic ribbon joint flattening system characterized by including: an upper cover die positioned above the lower cover die so as to face each other in the vertical direction with respect to the lower cover die.

18. In Paragraph 17, The lower cover die is installed in a fixed position so that its relative position with respect to the optical fiber supply line is maintained at a constant level, and an optical fiber receiving groove is formed in the central part of the lower cover die to accommodate a plurality of optical fibers in a seated state. A fiber optic ribbon joint flattening system characterized in that the upper cover die has a fiber optic cover groove formed therein that covers the upper region of a plurality of fibers received in the fiber optic receiving groove of the lower cover die.

19. In Paragraph 18, The optical fiber receiving groove of the lower cover die and the optical fiber cover groove of the upper cover die are formed such that their cross-sectional widths correspond to each other, and A fiber optic ribbon joint flattening system characterized by forming a void space between the fiber optic receiving groove and the fiber optic cover groove through which a plurality of optical fibers can pass while the lower cover die and the upper cover die face each other.

20. In Paragraph 19, A fiber optic ribbon joint flattening system characterized in that the height of the above-mentioned empty space is greater than the outer diameter of the optical fiber.

21. In Paragraph 19, A fiber optic ribbon joint flattening system characterized in that the fiber optic cover groove of the upper cover die is positioned higher than the fiber optic.

22. In Paragraph 16, A void space is formed in the above-mentioned flattening cover die through which a plurality of optical fibers can pass, and The height of the above empty space is greater than the outer diameter of the optical fiber, and A fiber optic ribbon joint flattening system characterized in that the upper surface of the above empty space is positioned higher than the fiber optic cable.

23. In Paragraph 16, A fiber optic ribbon joint flattening system characterized by having (N-1) resin dispensers when the plurality of optical fibers are composed of N optical fibers (N is a natural number greater than or equal to 2).

24. A step of manufacturing an optical fiber ribbon by joining the plurality of optical fibers side by side by forming a plurality of joints at spaced positions between the plurality of adjacent optical fibers; An optical cable core forming step for assembling a plurality of optical fiber ribbons formed in the optical fiber ribbon manufacturing step; and, A cable jacket covering step for supplying the optical cable core formed in the optical cable core forming step and covering the cable jacket; is included. The above optical fiber ribbon manufacturing step is, Optical fiber supply step in which a plurality of optical fibers are arranged parallel along the length direction and supplied to an optical fiber supply line in a predetermined direction; A resin injection step of injecting bonding resin between multiple adjacent pairs of optical fibers of the plurality of optical fibers; A bonding molding step for flattening the surface of bonding resin sprayed between the plurality of adjacent optical fiber pairs; and A method for manufacturing an optical cable characterized by including a resin curing step in which heat or ultraviolet (UV) rays are irradiated onto a bonding resin with a resin curing device to form a bonded portion, wherein the bonding resin having a flattened surface is irradiated with heat or ultraviolet (UV) rays.

25. In Paragraph 24, A method for manufacturing an optical cable, characterized in that, in the above-mentioned joint forming step, the highest point of the joint is flattened so as to be positioned above a connected straight reference line while simultaneously contacting each outer surface of a pair of optical fibers on both sides of the joint.

26. In Paragraph 24 In the above optical cable core forming step, the plurality of optical fiber ribbons are divided into a plurality of tube members or binders and assembled to form a plurality of optical units, and A method for manufacturing an optical cable characterized by assembling the above plurality of optical units to form the optical cable core.

27. In Paragraph 24, A method for manufacturing an optical cable characterized in that the above-mentioned joint forming step is manufactured by a flattening cover die applying pressure to the joint resin.

28. In Paragraph 27, The above flattening cover die is, A lower cover die that supports a plurality of optical fibers from below, positioned on the optical fiber supply line and moving along the optical fiber supply line; and A method for manufacturing an optical cable characterized by including: an upper cover die positioned above the lower cover die so as to face each other in the vertical direction with respect to the lower cover die.

29. In Paragraph 28, A method for manufacturing an optical cable characterized by flattening the surface of a bonding resin sprayed onto the plurality of optical fibers as the plurality of optical fibers pass through the space between the lower cover die and the upper cover die.

30. In Paragraph 28, The lower cover die is installed in a fixed position so that its relative position with respect to the optical fiber supply line is maintained at a constant level, and an optical fiber receiving groove is formed in the central part of the lower cover die to accommodate a plurality of optical fibers in a seated state. A method for manufacturing an optical cable, characterized in that the upper cover die has an optical fiber cover groove formed therein that covers the upper region of a plurality of optical fibers received in the optical fiber receiving groove of the lower cover die.

31. In Paragraph 30, The optical fiber receiving groove of the lower cover die and the optical fiber cover groove of the upper cover die are formed such that their cross-sectional widths correspond to each other, and A method for manufacturing an optical cable characterized by forming a void space between the optical fiber receiving groove and the optical fiber cover groove through which a plurality of optical fibers can pass while the lower cover die and the upper cover die face each other.

32. In Paragraph 27, A method for manufacturing an optical cable, characterized in that the outer surface of the joint portion of the optical fiber ribbon flattened by the flattening cover die has a smooth portion and two connecting portions respectively disposed on both sides of the smooth portion, and is pressed to form a curved shape.

33. In Paragraph 27, The magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die is the arithmetic average roughness (R) of the smooth portion formed on the outer surface of the junction according to JIS B0601 standard. a A method for manufacturing an optical cable characterized by controlling the ) to be 2 micrometers (μm) or less.

34. In Paragraph 24, One or more coating layers of the optical fiber include a coloring layer as the outermost layer, and The optical cable is characterized in that the above optical fiber ribbon manufacturing step involves manufacturing the coloring layer of the optical fiber in a process atmosphere with an oxygen concentration of 300 ppm or less.

35. In Paragraph 27, The magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die is the height difference (H) between the highest point of the junction and the straight reference line (L) connected by simultaneously contacting each outer circumference of a pair of optical fibers on both sides of the junction. UP A method for manufacturing an optical cable characterized by controlling the size to be 30 micrometers (μm) or less.

36. In Paragraph 27, The magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die is the height difference (H) from the lowest point based on a straight reference line (L) connected by simultaneously contacting each outer circumference of a pair of optical fibers on both sides of the junction. DN A method for manufacturing an optical cable characterized by controlling the ) to be 30 micrometers (μm) or less.

37. In Paragraph 27, A method for manufacturing an optical cable, characterized in that the magnitude of the pressure applied to the outer surface of the junction of the optical fiber ribbon by the flattening cover die is controlled such that the angle formed by the line connecting the end of each connection formed on the outer surface of the junction and the center of the optical fiber, and the line perpendicularly connected to the straight reference line that simultaneously contacts the outer circumference of each pair of optical fibers on both sides of the junction from the center of each optical fiber, is in the range of -30 degrees (˚) to -1 degree (˚).

38. In Paragraph 27, A method for manufacturing an optical cable, characterized in that the magnitude of the pressure applied to the outer surface of the joint of the optical fiber ribbon by the flattening cover die is controlled such that the angle formed by the line connecting the end of each connection formed on the outer surface of the joint and the center of the optical fiber, and the line perpendicularly connected to the straight reference line that simultaneously contacts the outer circumference of each pair of optical fibers on both sides of the joint from the center of each optical fiber, is in the range of 1 degree (˚) to 40 degrees (˚).

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